pagination.md

Resource collection and pagination

Motivation

Calling for a API resource collection usually mean dealing with pagination. This mean that one API call isn't supposed to return every element of the collection. Then, it may be handy to have objects and services in order the ease paginated collection iteration.

Description

• The Collection object holds either the partial collection view and the pagination metadata.
• The PaginatedCollectionIterator can be used to iterate over the whole collection by doing internally the HTTP calls.

Example

Collection object

use App\Dto\ProductDto;
use Mtarld\ApiPlatformMsBundle\Collection\Collection;
use Mtarld\ApiPlatformMsBundle\HttpClient\GenericHttpClient;
use Mtarld\ApiPlatformMsBundle\Microservice\MicroservicePool;
use Symfony\Component\Serializer\SerializerInterface;

class ProductService
{
    private $serializer;
    private $httpClient;
    private $microservices;

    public function __construct(
        SerializerInterface $serializer,
        GenericHttpClient $httpClient,
        MicroservicePool $microservices
    ) {
        $this->serializer = $serializer;
        $this->httpClient = $httpClient;
        $this->microservices = $microservices;
    }

    /**
     * Count the whole collection
     */
    public function countProducts(): int
    {
        $productMicroservice = $this->microservices->get('product');
        $response = $this->httpClient->request($productMicroservice, 'GET', '/products');

        /** @var Collection $products */
        $products = $this->serializer->deserialize($response->getContent(), Collection::class.'<'.ProductDto::class.'>', $productMicroservice->getFormat());
        
        return $products->count();
    }

    /**
     * Iterate over one page
     */
    public function getProductsName(int $page): iterable
    {
        $productMicroservice = $this->microservices->get('product');
        $response = $this->httpClient->request($productMicroservice, 'GET', '/products?page='.$page);

        /** @var Collection $products */
        $products = $this->serializer->deserialize($response->getContent(), Collection::class.'<'.ProductDto::class.'>', $productMicroservice->getFormat());
        
        foreach ($products as $product) {
            yield $product->getName();
        }
    }

    /**
     * Get pagination information
     */
    public function isLastPage(int $page): bool
    {
        $productMicroservice = $this->microservices->get('product');
        $response = $this->httpClient->request($productMicroservice, 'GET', '/products?page='.$page);

        /** @var Collection $products */
        $products = $this->serializer->deserialize($response->getContent(), Collection::class.'<'.ProductDto::class.'>', $productMicroservice->getFormat());
        
        return $products->getPagination()->getCurrent() === $products->getPagination()->getLast();
    }
}

PaginatedCollectionIterator service

use App\Dto\ProductDto;
use Mtarld\ApiPlatformMsBundle\Collection\Collection;
use Mtarld\ApiPlatformMsBundle\Collection\PaginatedCollectionIterator;
use Mtarld\ApiPlatformMsBundle\HttpClient\GenericHttpClient;
use Mtarld\ApiPlatformMsBundle\Microservice\MicroservicePool;
use Symfony\Component\Serializer\SerializerInterface;

class ProductService
{
    private $serializer;
    private $httpClient;
    private $microservices;
    private $collectionIterator;

    public function __construct(
        SerializerInterface $serializer,
        GenericHttpClient $httpClient,
        MicroservicePool $microservices,
        PaginatedCollectionIterator $collectionIterator
    ) {
        $this->serializer = $serializer;
        $this->httpClient = $httpClient;
        $this->microservices = $microservices;
        $this->collectionIterator = $collectionIterator;
    }

    /**
     * Iterate over the whole collection
     */
    public function getProductsDtoCollection(): iterable
    {
        $productMicroservice = $this->microservices->get('product');
        $response = $this->httpClient->request($productMicroservice, 'GET', '/products');

        /** @var Collection $products */
        $products = $this->serializer->deserialize($response->getContent(), Collection::class.'<'.ProductDto::class.'>', $productMicroservice->getFormat());
        
        yield from $this->collectionIterator->iterateItems($products);

        // You can also iterate over pages
        foreach($this->collectionIterator->iteratePages($products) as $page) {
            yield from $page;
        }
    }
}